Method of making a self-staking insert



Sept. 3, 1968 A- R. BREED ARTHUR R. BREED ATTORNEYS Unitcd States Patent 3,399,409 METHOD OF MAKING A SELF-STAKING INSERT Arthur R. Breed, Euclid, Ohio, assignor to The Lamson & Sessions Co., Cleveland, Ohio, a corporation of Ohio Filed Feb. 10, 1966, Ser. No. 526,506 8 Claims. (CI. 10-86) The' present invention relates to a metal insert for sheet or plate members and more particularly to a selfstaking type of insert.

In the type of insert to which the present invention relates, a portion of the insert is received in an opening the plate or sheet member and another part of the insert indents the sheet or plate member to cause material to flow around the first part to securely hold the insert against both removal and rotation. Certain structures of the prior art have utilized inserts with sharp edged grooves or knurls which bite into the material of the sheet or plate member for holding the insert against removal and rotation relative to the member. Such sharp edged structures cause stress concentrations in the sheet or plate which cause early propagation of fatigue cracks when the plate or sheet member is dynamically loaded. Moreover, the structures have not been adapted for use as punches and have not provided a noncircular body configuration where metal is flowed into substantially full circumferential contact with the body.

An object of the present invention is the provision of a new and improved method of cold forming a product which includes a body portion having an axially extending wall forming a periphery thereof and a projecting portion extending laterally from the wall in which the product is formed by upsetting an axially extending skirt portion at an end of the projection to flow the material of the skirt portion axially along the wall and laterally outwardly therefrom.

Another object of the present invention is the provision of a new and improved method of cold forming a product which has an annular body portion with an axially extending wall forming a periphery thereof and a laterally extending projection adjacent the aforementioned end of the body portion, and in which an axially extending skirt portion projecting as a continuation of the wall is deformed to cold flow the material of the skirt portion along the wall and laterally outwardly therefrom to form the projection without distorting the annular opening.

Another object of the present invention is the provision of a new and improved method of cold forming an annular member having a head portion and a body portion with an axially extending wall, and an enlarged portion adjacent one end of the body extending laterally from the wall, and in which an axially extending skirt portion formed at the aforementioned one end of the body constituting a projection of the wall and having a smaller cross-sectional area than the body is upset to flow the material of the skirt portion axially along the wall of the body portion and alterally therefrom to form the enlarged portion without distorting the annular opening.

Another object of the present invention is the provision of a new and improved method of forming an annular member as defined in the next preceding paragraph and in which the skirt is formed on an outer peripheral wall of the body portion and is cold flowed laterally outwardly therefrom to form the enlarged portion.

Further objects and advantages of the present invention will be apparent from the followin description thereof made with reference to the accompanying draw- 3,399,409 Patented Sept. 3, 1968 ings forming a part of the present specification for all subject matter disclosed therein and in which:

FIG. 1 is an elevational view with parts in section showing a self-staking nut embodying the present invention and a parent member for receiving the nut;

FIG. 2 is viewed looking from approximately line 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view taken approximately along line 3-3 of FIG. 1 but showing the nut in assembled relationship;

FIG. 4 is an elevational view with parts in section showing a nut embodying the present invention to prepunch its receiving opening in a parent member;

FIG. 5 is a cross-sectional view of tooling for cold forming the nut blank for the nut shown in FIG. 1;

FIGS. 6 and 7 illustrate upsetting operations during the manufacture of the nut in FIG. 1; and

FIG. 8 is an elevational view of a modified form of a self-staking plug nut embodying the present invention with parts in section.

Referring to the drawings, the insert shown therein is a self-staking nut 10 having a head portion 12 and a central projection 13 adapted to be received in a prepunched opening or in a self-punched opening in a sheet or plate member into which the nut is to be attached. The head portion 12 extends laterally outwardly of the projection 13 at one end of the nut and a tapped opening 14 extends axially through the head portion 12 and the central projection 13. conventionally, the outer side of the head portion 12 of the nut is considered the top of the nut.

The central projection 13 of the nut has a shank portino 13a which joins the head portion 12. The shank portion 13a, in cross section, has a polygonal configuration providing a continuous perpiheral surface which is adapted to hold the plug nut against rotation when the nut is inserted into a plate or sheet member. In the illustrated and preferred embodiment, the polygonal configuration is that of a regular polygon having included angles between adjacent sides which are obtuse. In the preferred practice of the present invention, the regular polygon is such that a circle inscribing the polygon has a diameter no smaller than of the diameter of the circle circumscribing the polygon and the diameter is no greater than that which will provide a three-thousandths inch clearance as a minimum between a side of the polygon and the circle circumscribing the polygon. The included angle between adjacent sides of the polygon may be as small as about but preferably the shank portion 13a is at least hexagonal so that the included angle between adjacent sides is It will be noted that in the type of regular polygon described, the sides of the polygon form chords of the circle circumscribing the polygon. While the sides of the polgonal shank portion are planar, adjacent sides are joined by arcuately curved surfaces which provide the aforementioned continuous peripheral surface. The peripheral surface is termed continuous, since the shank portion is constructed so that there is no point on the periphery formed by the intersection of planar surfaces, that is, there are no portions of the periphery formed by a line.

The lower end of the polygonal shank portion 13a flares out outwardly and blends with a bulge portion 18 on the central projection. The polygonal sides of the shank portion 13a preferably extend along the bulge portion 18 to a point at which the diametricalextent of the bulge is maximum. The bulge 18 therefore has the same general crosssectional configuration as the shank portion 13a. The central projection tapers from the bulge portion 18 to the outer end face 20 of the projection. The outer end face of the projection 13 is preferably more circular than the polygonal part of the projection and in the preferred and illustrated embodiment the portion of the projection immediately adjacent the outer end is generally frustoconical in configuration and tapers outwardly to the maximum transverse dimension of the projection at the bulge 18. The taper of the frusto-conical portion, designated by the reference numeral 21, preferably extends at a maximum angle of about 15 with respect to the axis of the tapped opening. It will be noted that the tapered portion extends higher at the corners of the polygon than at the flats.

The underside of the head portion 12 includes a planar circumferentially continuous surface engageable with the plate or sheet member as the nut is inserted therein to effect flowing of the material of the plate or sheet into engagement with the periphery of the projection 13. In the preferred embodiment the underside of the head portion 12 is provided with an annular recess 22 immediately adjacent the central projection 13 which defines an indenting flange 23 having an annular surface 23a immediately outwardly of the recess 22. The recess 22 opens downwardly and the bottom thereof curves upwardly away from the annular surface 23a and then downwardly to blend with the central projection. The radius of curvature of the bottom of the curved recess is smaller immediately adjacent the projection and becomes progressively larger I to provide a side surface 24 on the indenting flange which extends inwardly from the annular surface 23a and which is inclined to face toward the central projection 13.

The recess 22 causes the indenting forces to be concentrated at the annular bearing surface 23a on the indenting flange and this surface is designed to have an area such that the normal punching pressure will overcome the yield resistance of the material to permit the indenting flange 23 to indent itself into the material and to flow the material laterally to flow around and engage the polygonal projection 13 for substantially the entire circumferential extent thereof. The inclined surface 24 of the indenting flange 23 will aid in directing the flow of material inwardly against the polygonal portion.

It will be noted that the annular surface 23a, in the preferred embodiment, a continuous surface and therefore when the indenting flange is indented into the sheet or plate member, it not only causes a flow into engagement with the projection for substantially the entire circumferential extent of the projection but it does not tend to set up undesirable stress concentrations in the receiving member. Moreover, the nature of the polygonal central projection 13 is such that the adjacent sides do not define sharp corners which tend to set up stress concentrations. The included angles between the sides of the central projection 13 are obtuse angles which tend to minimize stress concentrations. While the central projection preferably approaches circularity, the angle between adjacent sides is such that the projection will securely hold the nut against rotation in the sheet or plate member.

The length of the porjection 13 is such that the end face 20 is preferably flush with or within the sheet or plate member when the nut is inserted into the member as is shown in FIG. 3. During insertion, the nut is backed by an anvil 26 or die member.

A self-staking nut embodying the present invention may be modified for use with a parent member having a counter-sunk receiving opening. Such a modified nut is illustrated in FIG. 8. The nut 10 comprises a head portion having an indenting flange 23 which is formed to permit the nut, in its assembled condition, to be flush with the surface of a sheet or plate member having a prepunched counter-sunk receiving opening. The indenting flange 23' includes a continuous annular bearing surface 23a extending between the projection 13' and an p y verging frusto-conical surface 23b which is formed to correspond with the frusto-conical counter-sunk receiving opening in the parent member. The bearing surface 23a provides a controlled indenting area such that as the nut is advanced into the receiving opening the bearing surface will engage and indent the frusto-conical wall of the counter-sunk opening to flow the material of the parent member into engagement with the periphery of the projection 13'. The projection 13 of the nut 10 is of the same construction as the projection 13 of the nut 10, previously described.

Conventional dies and punches are commonly used to prepunch openings in sheet metal or plate members for receiving the nuts. Rather than using a punch to prepunch a receiving hole, the nut itself may be used with the conventional punch die to punch the receiving opening for the nut as is illustrated in FIG. 4. The punch die will have a nominal opening approximately the same as the nominal opening of the opening to be punched and the outer end face 20 of the polygonal projection 13 is designed to cooperate as a punch with the punch die.

As stated above, the outer end portion of the central I projection is preferably more circular than the polygonal shank portion and the circularity is such that the clearance between the outer end of the projection and circular die is preferably not more than 10% of the thickness of the sheet material to assure clean punching. It will be understood that the projection 13 is not actually received in the die during punching since it does not project outwardly of the plate or sheet member. The clearance specified however is lateral clearance which would be present if the outer end of projection were disposed at the outer end of the opening in the punch die.

By providing the described polygonal configuration on the shank portion of the projection 13, maximum strength is obtained in the projection 13 for acting as a punch in cooperation with the punch die even though the shank portion is used to hold the inert against rotation. This enables nuts or other inserts embodying the present invention to be used to punch receiving openings in materials of considerable greater thickness than heretofore possible.

To provide maximum strength in the nut, the nut is preferably a cold forged nut. One of the problems confronting the industry in forming a cold forged nut as described is the problem of providing both the head portion and the bulge 18.

It has been found that the nut may be formed by first cold forging a metal slug in a die cavity to form a blank 29 with the general exterior configuration of the nut without the bulge 18 but with an axially extending skirt 32 which is polygonal in configuration to correspond to the shank portion.

Referring to FIG. 5, a die cavity 30 is illustrated which has a configuration for forming, in cooperation with a punch 31, a blank 32 having the exterior configuration of the nut without the bulge 18. The die cavity has a polygonal recess 33 in the bottom of the die cavity and forming an extension of the sides of the cavity for forming the axially extending polygonal skirt 32a about the periphery of the outer end of the central projection of the nut blank which is to be upset to form the bulge 18. As illustrated in FIG. 5, the punch member in cooperation with a projection in the die cavity also forms the central opening through the blank except for a web portion 35.

The blank formed in the die cavity 30 is removed from the die cavity 30 by moving the blank axially out of the cavity and the web portion may then be removed by a suitable punching operation. After the web portion is removed, the skirt is upset with an upsetting member 36 which is moved against the end of the blank while the sides of the blank are substantially unrestrained. The upsetting member is illustrated in FIG. 6 and has a flanged portion defining the 15 taper to control the flow of the material in the skirt to form the bulge. Initial attempts in upsetting the entire end of the blank to provide the bulge did not provide a satisfactory bulging without a distortion of the axial opening but when the circumferential skirt was provided adjacent the outer periphery of the outer end of the central projection 13 and this skirt upset with an upsetting member having a wall defining the frusto-conical portion 21, it was found that a highly satisfactory bulge was formed without distorting the axial opening.

While the preferred embodiments of the present invention have been described in considerable detail, it is to be understood that the invention is not to be considered to be limited to the precise constructions shown. A selfstaking nut could be constructed, for example, by providing a continuous peripheral surface on the body thereof which is configured to provide a sinusoidal periphery. It is my intention to cover hereby all constructions, modifications and arrangements which fall within the ability of those skilled in the art and the scope and spirit of the present invention.

Having described my invention, I claim:

1. The method of cold forming a product having an axially extending opening therethrough and portions projecting laterally from axially extending surfaces at opposite ends of the product and providing surfaces which face each other comprising the steps of cold forming a blank in a die cavity to form one of the laterally projecting portions of the product and an axially extending skirt of substantially smaller cross-sectional area than that of the blank and which extends axially from the blank at the opposite end from said one laterally projecting portion with the skirt generally forming a continuation of the axially extending surface from which the other of the portions is to project, removing the blank from the cavity by moving the blank axially with said one end leading, engaging the blank with a second die, and applying pressure to said skirt with said second die to cold flow the skirt laterally and toward said one portion to form the other portion.

2. The method of cold forming a product having an axially extending opening therethrough and portions projecting laterally from axially extending surfaces at opposite ends of the product and providing surfaces which face each other comprising the steps of cold forming a blank in a die cavity to form one of the laterally projecting portions of the product, a polygonal portion extending from said one laterally projecting portion, and an axially extending skirt of substantially smaller cross-sectional area than that of the blank and which extends axially from the blank at the opposite end from said one laterally projecting portion with the skirt generally forming a continuation of the axially extending surface from which the other of the portions is to project, removing the blank from the cavity by moving the blank axially with said one end leading, and cold flowing the skirt laterally and toward said one portion to form the other portion, said skirt being displaced to form an end portion which tapers from an end face of the blank outwardly toward said one laterally projecting portion and is of generally round cross section.

3. The method of cold forming an insert having an axially extending opening therethrough, a head portion extending laterally from a projecting body portion of the insert at a first end thereof and a bulge extending laterally from an axially extending surface of the projecting portion at a second end thereof, comprising the steps of forming a blank in a die cavity to form the laterally extending head portion of the insert and the projecting portion, said projecting portion having an axially extending skirt of substantially smaller cross-sectional area than that of the projecting portion at the second end thereof and surrounding an opening in the blank, the skirt portion generally forming a continuation of the axially extending surface of the projecting portion from which the head portion projects, applying pressure to the second end of the blank to flow the material of the skirt portion laterally of the projecting portion and toward the head portion along the axially extending surface, and allowing a portion of the material of said projecting portion to freely flow laterally outwardly under the influence of said axial pressure to form in an unrestrained manner a portion of said bulge which is closest to said head portion.

4. The method of cold forming an insert having an axially extending opening therethrough, a head portion extending laterally from a projecting body portion of the insert at a first end thereof and a bulge portion extending laterally from an axially extending surface of the projecting portion at a second end thereof, comprising the steps of forming a blank in a die cavity to form the laterally extending head portion of the insert and the projecting portion, said projecting portion having an axially extending skirt of substantially smaller cross-sectional area than that of the projecting portion at the second end thereof and surrounding an opening in the blank, the skirt portion generally forming a continuation of the axially extending surface of the projecting portion from which the head portion projects, applying pressure to the second end of the blank to flow the material of the skirt portion laterally of the projecting portion and toward the head portion along the axially extending surface, said step of applying pressure to the second end of the insert including the steps of confining the flow of material of the skirt portion and directing the flow thereof laterally of the axially extending surface to form the bulge portion.

5. The method as defined in claim 4 wherein the step of confining the How of material of the skirt portion includes the steps of providing a frusto-conical surface surrounding the skirt portion and guiding the flow of material of the skirt portion along said frusto-conical surface to provide the bulge portion with a tapered surface portion adjacent the second end of the insert.

6. The method of cold forming an insert having an axially extending opening therethrough, a head portion extending laterally from a projecting body portion of the insert at the first end thereof and a bulge portion extending laterally from an axially extending surface of the projecting portion at a second end thereof, comprising the steps of forming a blank in a die cavity to form the laterally extending head portion of the insert and the projecting portion, said projecting portion being noncircular in cross section and having an axially extending skirt of substantially smaller cross-sectional area than that of the projecting portion at the second end thereof and surrounding an opening in the blank, the skirt portion generally forming a continuation of the axially extending surface of the projecting portion from which the head portion projects, applying pressure to the second end of the blank to flow the material to the skirt portion laterally of the projecting portion and toward the head portion along the axially extending surface, said skirt being displaced to form a bulge portion which tapers from the second end of the blank outwardly toward said head portion and is of generally circular cross section.

7. The method of forming an insert with a bulge in its end, said method comprising the steps of providing a blank having a shank with a laterally projecting head at one end and an end portion of substantially smaller cross section than said shank extending axially from another end of said shank and forming a continuation of an axial surface of said shank, said blank having an' opening extending axially through said end portion and into said shank, applying an axial force to said end portion to cold flow material forming said blank laterally outwardly and axially toward said head portion, confining the laterally outward flow of material adjacent to application of said axial force with a surface which slopes outwardly toward said head of said blank to provide a flaring outwardly of the material in the direction of material flow and toward a maximum dimension of said bulge, and allowing the material ahead of the material confined by said surface 7 8 to flare outwardly in an unrestrained manner to cause an References Cited outward flaring of material in a direction opposite to the UNITED STATES PATENTS direction of material fiow and toward the maximum dimgnsion of aid Darhng T 8. A method as set forth in claim 7 wherein said shank 5 1,883,906. 10/1932 Hflsselqulst 10-86 1,925,753 9/1933 Fitch et a1 10-86 is noncircular in cross-section and said surface is frustroconical in shape to form a portion of said bulge which is generally circular in cross-section. LEONIDAS VLACHOS Prima'y Examiner 

1. THE METHOD OF COLD FORMING A PRODUCT HAVING AN AXIALLY EXTENDING OPENING THERETHROUGH AND PORTIONS PROJECTING LATERALLY FROM AXIALLY EXTENDING SURFACES AT OPPOSITE ENDS OF THE PRODUCT AND PROVIDING SURFACES WHICH FACE EACH OTHER COMPRISING THE STEPS OF COLD FORMING A BLAND IN A DIE CAVITY TO FORM ONE OF THE LATERALLY PROJECTING PORTIONS OF THE PRODUCT AND AN AXIALLY EXTENDING SKIRT OF SUBSTANTIALLY SMALLER CROSS-SECTIONAL AREA THAN THAT OF THE BLANK AND WHICH EXTENDS AXIALLY FROM THE BLANK AT THE OPPOSITE END FROM SAID ONE LATERALLY PROJECTING PORTION WITH THE SKIRT GENERALLY FORMING A CONTINUATION OF THE AXIALLY EXTENDING SURFACE FROM WHICH THE OTHER OF THE PORTIONS IS TO PROJECT, REMOVING THE BLANK FROM THE CAVITY BY MOVING THE BLANK AXIALLY WITH SAID ONE END LEADING, ENGAGING THE BLANK WITH A SECOND DIE, AND APPLYING PRESSURE TO SAID SKIRT WITH SAID SECOND DIE TO COLD FLOW THE SKIRT LATERALLY AND TOWARD SAID ONE PORTION TO FORM THE OTHER PORTION. 